1. The Field of the Invention
The present invention relates to compositions and methods of manufacture of compressed powder matrixes for medicaments used in the transmucosal delivery of the medicaments. More particularly, the present invention is directed to compositions, and methods and apparatus for producing such compositions, for non-invasive administration of precise amounts of medicaments through the mucosal tissues of the mouth, pharynx, and esophagus.
2. The Background of the Invention
Recently, numerous advancements have taken place in the field of pharmacology with respect to the administration of drugs to treat various conditions. Despite the tremendous advancements in the field, however, drugs continue to be administered using substantially the same techniques that have been used for many decades. The vast majority of pharmaceutical agents continue to be administered either orally or by injection. Nevertheless, it is frequently found in the art that neither of these administration routes are effective in all cases, and both administration routes suffer from several disadvantages.
Oral administration is probably the most prevalent method of administering pharmacological medicaments. The medicament is generally incorporated into a tablet, capsule, or a liquid base, and then swallowed. The oral administration modality is often preferred because of its convenience. In addition, oral administration is generally nonthreatening, painless, and simple to accomplish for most patients.
Nevertheless, oral administration of drugs suffers from several disadvantages. One disadvantage is that pediatric and geriatric patients frequently have difficulty swallowing pills, and such patients often refuse to cooperate in swallowing a liquid medication. In addition, for many medicaments, the act of swallowing the medicament increases gastric volume and the likelihood of nausea and vomiting; this is a particularly dangerous condition for patients prior to anesthesia.
A further problem with oral administration is that the rate of absorption of the drug into the bloodstream after swallowing varies from patient to patient. The absorption of the drug is dependent upon the movement of the drug from the stomach to the small and large intestines and the effects of secretions from these organs. Anxiety and stress can dramatically reduce these movements and secretions, prevent or reduce the final effects of the drug, and delay onset of the drug's effects.
Most significant is the fact that there is normally a substantial delay between the time of oral administration and the time that the therapeutic effect of the drug begins. As mentioned above, the drug must pass through the gastrointestinal system in order to enter the bloodstream; this typically takes forty-five minutes or longer. As mentioned above, anxiety and stress often increase this delay.
For many applications, such as premedication before surgery or where immediate relief from pain or a serious medical condition or immediate effectiveness of the drug is required, this delay is unacceptable. In modern outpatient units and operating rooms where rapid turnover of patients is essential for cost containment, extensive delays in the action of a drug are simply unacceptable.
An additional disadvantage of oral administration is that many drugs, particularly drugs with central nervous system ("CNS") or cardiovascular action, are almost immediately metabolized. The veins from the stomach and the small and large intestines pass directly through the liver. Thus, drugs entering the bloodstream must first pass through the liver before distribution into the general blood circulation. More than sixty percent of most drugs (and essentially one hundred percent of certain drugs) are removed from the patient's bloodstream during this "first pass" through the liver. The result is that oral administration is impractical for many drugs, particularly most central nervous system and cardiovascular-acting drugs that are used in critical care situations, as a premedication prior to surgery, or for the induction of anesthesia.
Further, additional stress is placed on the liver as it removes the excess drug from the bloodstream. This is particularly severe if the cardiovascular or renal vascular treatment has been occurring over an extended period of time. The liver may become overloaded with the drug's metabolite which then must be excreted in the patient's urine. As a result, there is an increased risk of hepatic or renal disorders.
Another difficulty encountered in administering drugs orally is that dosages are prepared or determined for use with an "average" patient. Most drugs have widely varying effects on different patients. These effects depend upon patient habits, subtle genetic differences between patients, blood volumes, age, and numerous other known and unknown factors. Introducing a bolus of drug orally does not provide the ability to control the precise dose needed to obtain the desired effect, rather the dose is estimated in order to produce an average effect in an average patient. The result may be underdosing or overdosing a particular patient.
Underdosing a patient because of a low susceptibility to the drug fails to evoke the response sought by the physician. Overdosing the patient can result in dangerous depression of vital body functions, especially the heart and lungs. This can cause prolonged respiratory depression (necessitating mechanical ventilation after surgery), cardiac depression, and cardiac arrest.
In order to avoid some of the disadvantages of oral administration, injection is frequently used. Injecting a drug (generally intravenously or intramuscularly), results in rapid entry of the drug into the patient's bloodstream. In addition, this type of delivery avoids the removal of large quantities of the drug by the patient's liver. The drug instead becomes rapidly distributed to various portions of the patient's body before exposure to the liver.
Most patients, particularly children and geriatric adults, have an aversion to injections. In some patients, this aversion may be so pronounced as to make the use of injections a serious concern. Since intense psychological stress can exacerbate a patient's debilitated condition, it sometimes becomes undesirable to use injections where the patient is seriously ill or suffers from a debilitating condition or injury.
In addition, individual variations in susceptibility in the metabolism of various drugs (particularly drugs with central nervous system activity) are even more profound when utilizing the injection route. In order to prevent overdosing, it is the practice to inject a patient with a lower than average dose and then supplement the dose with additional injections as necessary. This "titration" makes necessary the use of repeated injections, which in turn greatly increases stress on the patient. Again, a precise dose cannot be administered to produce a precise effect because the patient's response varies widely depending on the specific characteristics of the specific patient.
One common approach to preparing a patient for surgery is to orally administer a sedative or anxiolytic. Although quick onset of sedation or anxiolysis has not always been a critical factor, it is more so now. Changing practices, including the increased use of outpatient units for day surgery and the pressures for cost containment in modern medicine, dictate rapid onset of action and the use of an absolutely ideal dose in order to avoid increased costs of caring for patients with delayed recovery secondary to slightly overdosing with anesthesia. Oral administration of premedication drugs with central nervous system activity (which cause a rapid onset of sedation and anxiolysis without producing excessive sedation) is difficult to accomplish.
Some investigators have suggested that it may be possible to administer medication through the buccal mucosa of the cheek pouch or by sublingual administration. See, copending application Ser. No. 729,301, filed May 1, 1985, in the name of the inventors hereof, and entitled "METHODS AND COMPOSITIONS FOR NONINVASIVE ADMINISTRATION OF SEDATIVES, ANALGESICS, AND ANESTHETICS." Such administration through the mucosal tissues of the mouth, pharynx, and esophagus of therapeutic drugs possesses a distinct usefulness. Administration of drugs by this route does not expose the drug to the gastric and intestinal digestive juices. In addition, the drugs largely bypass the liver on the first pass through the body, thereby avoiding additional metabolism and/or inactivation of the drug.
Generally the drugs which are administered by any of the methods described above have an unpleasant taste. As a result, in order to allow for buccal or sublingual administration through the oral mucosal tissues, it is also necessary to incorporate the drug into some type of pleasant tasting mass, such as a "candy" matrix.
In the manufacture of medicated candy products by existing methods, the therapeutic agent is added to a molten candy mass. The resultant mixture is then thoroughly mixed to ensure proper distribution of the drug within the molten candy mass. The mixture is then poured while still molten and allowed to solidify into a semi-solid mass. Alternatively, the hot candy mass may be poured into molds, the size and shape of which may be determined as desired.
For effective application of the drug, the final candy product must contain the drug uniformly distributed throughout in order to ensure uniform levels of medication. Alternatively, for some applications, varying concentrations within known and controlled ranges may be desired to vary the rate of drug administration. Difficulties are encountered in attempting to blend solid drugs in a uniform or otherwise carefully controlled manner. Many drugs are insoluble, or only partially soluble, in one or more of the ingredients of the hard candy base. Thus, the resultant product is often found to be lacking in uniform distribution of the drug.
In addition, it is often found that when the temperature of the candy mass is increased in order to enable a more uniform distribution (generally to a temperature above approximately 230.degree. C.), considerable decomposition of the drug takes place. While the extent of decomposition may vary, high temperatures are generally undesirable in the handling and processing of medications. Thus, the process of formation of the candy product may itself degrade and/or inactivate the therapeutic agent.
Furthermore, many presently available medicated candy lozenges tend to crumble when placed in the mouth. As a result, uniform release of the drug into the mucosal tissues does not take place. Rather, the crumbled lozenge is mostly chewed, and swallowed, and the drug enters the bloodstream through the stomach and intestines as described above. Thus, it will be appreciated that candy lozenges have very definite limitations for use in the administration of a drug through the oral mucosal tissues. As a result, lozenges have not been used to administer potent, fast-acting drugs, such as drugs that affect the central nervous system, the cardiovascular system, or the renal vascular system.
While the administration of certain drugs through the oral mucosal tissues has shown promise, development of a fully acceptable method for producing a medication in a desirable form and administering the medication has been elusive. It has not been possible to develop an acceptable candy product for use with most drugs without heating the product to the point where degradation will be expected.
It should also be noted that pH conditions within the mouth tend to adversely affect the administration of certain drugs by the mucosal administration route. It has been found in the art that administration of drugs through the mucosal tissues occurs best when the drug is in the non-ionized form. Variations in pH affect drastically the percentage of the drug which is non-ionized at a particular point in time. As a result, the pH conditions within the mouth limit the effectiveness of certain drugs administered buccally or sublingually in that those conditions cause the drug to exist in the ionized form which is largely unavailable for transfer across the mucosal tissues.
In view of the foregoing, it would be an important advancement in the art of administering potent, fast-acting drugs, if suitable methods and compositions provided a precise dosage to a precise effect in every patient. It would be a related advancement in the art to provide such methods and compositions which avoided the disadvantages of overdosing, underdosing, and the immediate metabolism encountered in the "first pass effect," yet did not involve injection by needle into the patient.
It would be a further significant advancement in the art to provide methods and compositions for incorporating drugs (including insoluble drugs) into a soluble matrix without heating the mixture to the point that degradation occurs. It would be a related advancement in the art to provide such a method which provided the capability of uniformly incorporating insoluble drugs into the soluble matrix. It would be another advancement to provide methods of controlling pH during mucosal delivery of a drug such that the drugs exist primarily in the non-ionized form.
Such compositions and methods of manufacture are disclosed and claimed herein.